[ARM] pxa/z2: Fix flash layout typo

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>

arch/arm/mach-pxa/z2.c

@@ -164,7 +164,7 @@ static struct mtd_partition z2_flash_parts[] = {
 	}, {
 		.name	= "U-Boot Environment",
 		.offset	= 0x40000,
-		.size	= 0x60000,
+		.size	= 0x20000,
 	}, {
 		.name	= "Flash",
 		.offset	= 0x60000,